0:00 - Today I'm gonna show you something you've maybe never seen before, something I had never seen before that is completely fascinating. We're gonna take a look inside an espresso puck, "But how can you look inside an espresso puck?" You ask. Good question. We're gonna use a CT scanner. Now, you've probably heard of CT scanners mostly, I suspect, in a medical context, but they do have a bunch of industrial applications and we could turn their attention on to coffee. Now, I should explain how a CT scanner works. Firstly, we need an object. We should probably make this object a little bit more interesting though. (coffee beans tinkling) Now, you place your object inside your machine. Now, a CT scanner has an x-ray emitter on one side and a sensor on the other side. So it's taking a bunch of x-rays that will show you the density from each sort of angle
0:46 and then the machine rotates what's inside of it. And by rotating at a full 360 degrees, well, you can build a picture of this object in 3D space by density. That's the kind of computed part of CT, computed tomography. And then once you've done that, well, tomography is looking at a cross section. So you can take an object like this and sort of slice into it to reveal what's inside. You can even look at the same thing with different colors for different densities. It allows you to see incredible things. But what if we could do it with an espresso puck? What could we see? The downside is, of course, that here at the studio, I don't have a CT scanner. Fortunately for me, and I hope for you, I'm here in Cambridge, Massachusetts and I have a little bit of spare time
1:31 and that happened to sort of match up with Lumafield having a little bit of time for me. So Lumafield make CT machines that are kind of accessible, as in I can use and understand what they output, and they like coffee, and they said I could have a little play. Now, I should say at this point this video is not sponsored by Lumafield. They were incredibly generous with their time. They were busy people who gave up a lot of time and attention to help me for a day visiting there, for which I'm very grateful, but they're not kind of a sponsor of this video. Here was the plan. We were going to use the CT scanners that they had to try and assess what's going on in a puck when you distribute your coffee in different ways. And so, very kindly, a local person lent me a Decent espresso machine and a Monolith grinder and a few little coffee tools, everything I would really need to prep shots.
2:18 My thought was to use a Decent espresso machine to collect a bunch of data, potentially to go with, you know, the data that I got from the machine. As you'll find out a little bit later on in the video, this did reveal some slightly foolish thinking on my part and some mistakes that I made. But we'll... we'll get to that. Now, one of the challenges with CT scanning is time, because not all materials are created equal to the world of the x-ray. Now, if you take a portafilter, it's a big old piece of metal. And actually if you just take the basket, even this, this stainless steel basket, well, it's quite tricky to scan quickly. I'll try and explain it in a way that makes people who know about CT scanning not lose their minds for this sort of simplification of it. If you wanna scan quickly, then you have to have a relatively sensitive sensor.
3:06 If you think about photographs, the more light sensitive a camera needs to be, the grainier the image is going to be, as you'll see from this image, which is shot at a very high sensitivity with not much light. It looks pretty terrible. And this is equally true in CT scanning. If you are trying to scan very quickly, the chances are you'll get a very noisy image. Now, in the world of coffee, we're looking at teeny, teeny tiny pieces. Teeny tiny pieces, you know, a few microns in size, up to maybe 50, 60, 70, 80, 100 microns in espresso, but really very small. And so in the world of CT, you have what are called voxels, which is volume pixels, which is a kind of representation of these things and they get pretty small but certainly not as small as a singular fine coffee piece.
3:53 Which means that if you had a piece of noise in your image, then you wouldn't know if that was a piece of coffee or a piece of noise. To scan this would probably take 12 hours for a single scan in a metal basket. We tried to circumvent this by using a little 3D printed basket because that's actually much easier for x-rays to pass through and the coffee inside will become clearer than it would be inside a stainless steel basket. That doesn't mean it couldn't be done. It just practically speaking meant I would've gotten one or two scans from my entire day there. Now, as an added bonus going into their offices, I saw in the corner of their kitchen, a little Breville set up there with a built-in grinder. And this actually was completely perfect. To some extent, I maybe had too nice of a coffee setup with a Monolith grinder. It's a truly incredible grinder.
4:40 Having something much cheaper actually is the first thing I'm gonna show you, which is what comes out of a Breville 'cause I think it's a really nice representation of what you can see in a sort of dose of coffee with a CT scanner. Now, let me show you a very cool thing. This is our little puck of coffee from the Breville/Sage little grinder. You can see glorious clumps of coffee absolutely everywhere. We know in the world of espresso brewing that a big clump of coffee isn't really an ideal thing. Let's have a little closer look inside the whole thing. What we're gonna do is essentially push in now from the side and you'll see the basket and then you can see the clumps on the inside and you can see, this is so cool, clumps right the way through the basket.
5:27 Now, one thing I look at, as I sort of scrub through this whole basket, is actually, there's way more clumps around the edges of the basket, and around the top as well, than there are, kind of, right in the middle. I mean the fact that this is possible just absolutely delights me. Now, you're probably wondering what happens when you tamp them? This is a badly tamped one, I need to highlight that now. You'll see that the sort of nature of the tamper in that machine is that it's built-in and you're sort of lifting up to tamp against it. That meant that my tamp is both uneven and actually lacks sufficient pressure. As we scrub in here, you can see all of these little pockets of empty space and you can still see, if you watch carefully, you can still see clumps there, sort of gaps! This is not a bed of coffee that's gonna brew well.
6:13 Clumps definitely survive a bad tamping process. I think we've known this for a good long while. I think people know that if you've got a very clumpy grinder you should probably do some puck prep to get the best out of it. The Breville is a fun little extra in this whole thing. It wasn't really what I was there to investigate and have a look at. Recently and I think driven in part by Lance Hedrick, I think, more than anyone else, there's been a lot of discussion about ideal puck prep. Things like needle distribution tools have become quite common. I'm a fan of them, I think they're a good thing. And then the kind of grind into a shaking cup, one that you might get with some high-end grinders, that allow you to put lid on, shake it around a little bit and then dose from there. Well that was shown potentially to be a little bit, sort of better, in terms of better extraction outcomes, higher yields, maybe better tasting shots.
6:59 So that's what I wanted to look at. I had a very nice grinder, perhaps that was gonna be a help or a hindrance, and I wanted to see if I dosed straight into the basket versus dosed into the basket and then applied a distribution tool, (In this case it was the Barista Hustle AutoComb) or I dosed into a shaker, shook the grounds and then dosed them into the basket. Well, was there a significant difference in those pucks before and after tamping? So the first one out, we can have a look at this kind of sliced up model. This is no prep, so this was dosed straight from the grinder into the basket. And you'll see as we look at this, there's obviously not a particularly even distribution within the basket. There's a mound in the middle. That's pretty common. Now, you can settle by hand and I did settle a little bit by hand, giving it a gentle tap before brewing.
7:45 But as you look at this, as you sort of scrub through it, it doesn't look like there's any obvious clumps or issues with it. It does just seem, you know, poorly distributed before being tamped. As you look at this here, it's now been AutoCombed. You can't see any obvious kind of, or maybe a little bit, you can see some sort of spiral patterns in the top there. If we go and slice into it though, you can see these sort of vertical lines in the distribution where the needle was. That's quite surprising that they're that evident to feel like the needles are very, very, very small. And it does make me think that when I do needle distribution, you know I am leaving that pathway, to some extent, behind. And then you've got the shaker. Now, the shaker caught me off guard here. Just in the middle there, you can just see these little pockets of what look like higher density clumps,
8:32 reminiscent to some extent of the Breville clumps. When you've shaken the coffee, some of it seems to have stuck to itself. This feels very counterintuitive. This is obviously limited in its scope, in its testing. Was it the particular coffee that we were using? Was it my shaker technique? Was there something else at play? Or maybe they don't matter. Maybe it doesn't matter. Maybe we're worrying about things we don't need to worry about. We didn't brew these because they had to be scanned and they were obviously in these little PLA baskets that were very thin, very scannable. So I could never brew the exact thing that I scanned. Shall we have a look at them tamped? Because we looked at these at the time very quickly and we decided that for the tamped versions we would benefit from reducing the noise in the image
9:17 and going for a much longer scan. So the three tamped beds were scanned for 12 hours. So we will have a sort of a little bit more detail here. So we'll start with the Monolith, the no prep, but tamped bed now. And I love, just as this little side note, how cool the little tiny bits of coffee stuck to the edge of the basket look on this. It looks like there's not the world's greatest distribution in terms of variance of density here. As you scrub through, the density is a little bit lower at the top of the puck. I never thought about that. I always kind of presumed that it would be an equal density all the way through, but it does seem to me like the very top of a puck done this way is slightly less dense. Maybe someone who reads CT scans for a living will look at that and be like, "You're an idiot. You've got no idea what you're talking about."
10:04 It also actually looks a bit like the very bottom in the middle is slightly less dense. I'm not sure if that's just like a tiny artifact there. Anyway, just that's a surprising thing. But with the AutoComb, where we had those sort of vertical lines, well, can we see them afterwards? Don't take kind of color for color necessarily on this one. The way that you sort of prep an image for a view will mean that what's green in this image may not be green in a sort of different image. So don't be like, oh, this is less green, therefore it's less dense. That's not... don't do that. Just let's just look at what we've got. Now, this looks, I've gotta say, nice and even. I would say again, it looks like the top, what third potentially? Does look a little less dense.
10:51 I'm really genuinely interested in this and I don't know how you could do a practical test of this to work it out. It looks like there's a little sort of hollower pocket at the base as well. Again, could just be an artifact of the scan. It's hard to say for sure, but I don't see any of those vertical lines as I scrub through this, as I move through it, that - that isn't what I'm seeing. You are just gonna be thinking about channeling. I know you, you're looking at this, you're thinking, "What about channeling? Is that, is channeling inevitable? Can we never get true even distribution?" It's a good question, but let's have a little look at our shaker. Again, I'm gonna say it, top of the bed looks notably less dense on all of these and this one, it's also true. I've just never thought about this. What does this mean? Scrubbing through, I mean, there's no sign of the clumps, right?
11:36 Like there's no way you can see anything clumpy in there. Now, I did mention that I did a stupid thing. These sort of prepped beds are all well and good, but what you wanna see is a brewed bed of coffee. You wanna see a spent puck. I know you do. You wanna see, "Can I see the channel in a spent puck?" And chasing this, I pulled shots and I made sure that they channeled and they did channel, they did channel. And I was like, great, I have made a channel in a coffee puck. Can I see that in a CT scan? I'll tell you about that. But this isn't a sponsored video, but there is something I just wanna tell you quickly, about my new book, it's the third edition of "The World Atlas of Coffee." Originally came out in 2014. It's been updated and this edition is a significant update. About 40% of the book is new material. If you're not familiar with it,
12:21 it covers everything from the history of coffee, coffee itself into brewing better coffee and, of course, origin by origin explanations of how coffee arrived there, where it's grown, what kind of, you know, varieties you can expect, what kind of traceability you can expect, it's a little bit on taste, those kind of things too. We've said previously, if you have the first edition, you don't need to upgrade to the second edition and I would say if you have the second edition, I can't say you have to upgrade to the third. That's a ridiculous thing to say, even though this is a pretty big bump in what's out there. If you don't own this book, that's okay. I hope I can tempt you with it. I promise it will make coffee drinking a little bit more enjoyable, which is kind of the whole point of this thing and a little less confusing in the world of exploring coffee and specialty coffee in particular. It's a lovely gift if you're that way inclined too.
13:07 The easiest place to get this is probably gonna be Amazon and there is a link in the description down below. But if you can, please do support your local bookshops. If you want a signed copy, we have some stock in the US, shipping just to the US and if you're anywhere else in the world, we have stock at Square Mile. We're shipping from there in the release week. That's it. I don't wanna talk about this too much. It's a great way to support the channel. It's a great way to explore coffee further. Book. Here is a spent puck. In this case, you'll see it's on a little slip of paper because we still had to put it onto something to get it from the basket into the machine. So when you look at the scans, if you're wondering what the little line is, it's a bit of paper. Now, look at this, you're like, "That looks pretty cool. That's definitely a spent puck. That brings me pleasure to look at.
13:52 That's kind of fun. Let's have a little scrub inside." And then realization dawns immediately, because you look at this and you scrub through it and you're like, "Hang on a second. Why are all the lines and channels and pockets going sideways?" Now, some of you, I suspect a good number of you! Don't have to comment if it is you, I believe you. You've worked out what's gone wrong here, haven't you? The espresso machine is number one. Now, in most espresso machines, certainly higher-end espresso machines, at the end of a shot, when the shot finishes, there's still some pressure inside your portafilter. What many machines will do is open a valve to allow the pressure back out of the top through a tube into your waste, in your drain box usually. That's called a solenoid valve or a three-way valve.
14:40 And the minute you stop that shot, essentially the pressure goes from being down onto the puck through to the exact opposite, up, up, expansion happens. And that's exactly what you can see here. The minute that you stop a shot, all of these sort of cracks form horizontally because of the way that the puck is being stretched. And we will see this in all of the spent pucks that we looked at. There's a sort of double challenge here. So you could be like, okay, how do you fix this? You could use something like a lever machine. If you have a spring lever or a manual lever, they never have a pressure discharge valve on them. Once the spring has finished expanding, the pressure's gone. And so you'll never have that kind of expansion moment in a lever machine. And so I realize now if I had been able to do this again,
15:28 I would do it with a lever machine. But it's not just the machine that's causing the trouble. You've still got to get this puck out of the basket. Or do you? Well, in our case we did, we had to get it out of the basket because we couldn't scan in metal. There wasn't enough time. If you had one of these machines in your workspace, if I had one here, which I don't. I don't need one, it's ridiculous. I'd love one but I don't need one. Well, yes, you could spend 24 hours scanning a spent, undisturbed puck. You lift it out of a portafilter, used in a lever machine and you might see something. Maybe, maybe you'd see something. Now, this puck didn't particularly channel and you can see it looks striped for want of a better term. Let's have a quick look at a different puck.
16:13 What a delight. I love that the paper is so thin. And you can sort of see wisps of paper almost in there. Now, you see what would've happened here. There's a big chunk missing on this puck. Again, because as you knock a puck out, well, you've spent probably 30 seconds pressing that wet puck as hard as, you know, as a human, you could, harder in fact, nine bars of pressure, eight bars of pressure, whatever it is, against this metal basket. You pressed it really hard. So there's a bit of adhesion probably happening there. So when you knock a puck out, often you'll see a puck will break a little bit. I was as gentle as I could be here. I wasn't like slap, slap, slap, slap, slap. It was sort of a gentle, please just, just fall out, fall out for me nicely. You'll see the same thing here on this one, like, giant, look at that. Big old horizontal cracks in there.
16:59 It doesn't really look like anything vertical is obvious here, right? Now, this wasn't a channeled puck. I'll get to the channeled puck in a second, but you see all of the same issues in terms of we can't learn what we'd love to learn here. They did an extra cool thing here. This is a porosity display, which is pretty great and shows the kind of pore sizes. So you can see inside of the model where things sort of fell apart so to speak. I just think that looks kind of weird and cool and delightful. But let's look at the puck that definitely channeled. There it is, you can see again, a good chunk of it got stuck to the basket. Very irritating, very disappointing. Now, interestingly here, it does look like the middle of the puck is shallower, right? It doesn't look even right the way across.
17:46 And that's interesting. I wonder if that is why channeling happened. As I recall, the channel was fairly central. You can't see a line, you know, and when a channel happens, when a good channel happens, that's a good old spray of liquid, right? That's a decent amount of pressure is making it right through the puck to the sort of particular hole that it's spraying out of in the basket. But I just don't know if you can see it, you know. At best, I would say it does look like we've had a pocket of low density in the middle of the puck and that is where pressure has gotten through. And it looks like it's less dense at the top, almost like it was a sort of, as you look down on the puck in the portafilter, it was a sort of crater in there, because again, you can see it's where it's pressed against the basket, it's much smoother. At the bottom, you can see it's, you know,
18:31 where it was exposed to the water and the shower screen where it looks less even. But I don't know if you can see a channel. And I wish you could. And maybe you can. I will, if I get the chance, repeat this experiment with a machine without a solenoid valve with a lever machine, with very long scan times. Like really, I would probably run for, like, as long as the machine would let me, to try and get as much detail as possible because we're looking at really tiny pieces of stuff here. Like even when a coffee particle is swollen by water and you know, a little bit bigger, I guess, it's still a tiny, tiny thing. But, how cool is this to look at? Now, very kindly, Lumafield have set it up so that you can explore these models too if you want to.
19:19 I will leave links to each of them down below and there'll be kind of guidance to how you explore them, but you can mess around with them, open them in the browser. Once again, a massive thank you to Lumafield and the team there. Very busy, very smart people took a generous, incredible amount of time to hang out with me, mess around with this stuff and then help me afterwards to understand the data that we captured. They're very cool. I shall say a big thank you to them. Shout out to them being basically awesome. Go and check out their blog. I'll link to one of their blog posts, actually, that put me onto them because they'd scanned different roast levels and you can look at coffee beans from a light, a medium and a dark roast in a CT scanner. And it's cool! Anyway, thank you again to the support I had for getting a machine and a grinder there. You've very much appreciated. And John from Decent for setting up
20:05 the Decent Ambassador Program, also appreciated. That's it. The stuff that I mentioned is linked in the description down below. If there's something that you would like to see in the world of coffee, go into a CT scanner, leave a comment because maybe that can happen. If there's something you think it would reveal, that would be fascinating I would love to hear from you down in those comments below. But for now, I will say thank you so much for watching, and I hope you have a great day.
